Nikos Baxevanis

I build testing tools that find hard-to-catch bugs before systems go live. At the Stacks Foundation, I developed fuzzers and model-based testing tools that uncovered consensus flaws and denial-of-service conditions before a major network upgrade. I maintain Hedgehog, a property-based testing library that powered Echidna—the first smart-contract fuzzer for Ethereum. I work across Haskell, F#, .NET, Rust, and TypeScript, with a focus on input shrinking, reproducibility, and instrumentation. My experience scaling Web2 systems for acquired companies grounds my approach to reliability and security in blockchain protocol testing.

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Projects

2022 – present
Core contributor to rendezvous and madhouse-rs, fuzzing tools for Clarity and Rust. Helped identify issues during network upgrade testing and chain behavior under load.
2016 – present
Core contributor to Hedgehog — property-based testing for Haskell, F#, R, and Scala. Used in the early development of Echidna by Trail of Bits.
2017 – 2020
Ported SplitMix — a fast splittable PRNG. Based on work by Steele, Lea, and Flood. Passes all dieharder tests. Used in Hedgehog for replay and shrinking.
2011 – 2020
Ported dk.brics.automaton and xeger to create Fare — a library for generating regex-constrained strings. Used in AutoFixture and widely adopted as an alternative to Microsoft's Rex.
2011 – 2016
Core contributor to AutoFixture, a .NET testing library (3.5k+ stars). Helped shape AutoFixture 3, introduced novel features and tools like Fare. Project later submitted to the .NET Foundation.

Writing

2023-01-30 – Invariant testing from command-line
2022-03-15 – Clarity model-based testing primer
2022-03-05 – Clarity property-based testing primer
2020-03-30 – The rhyme of the altered parser
2017-04-10 – Less fragmented properties with Hedgehog
2016-02-08 – Write you some QuickCheck

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What others say

“I had the chance to work with Nikos on a challenging DeFi project in 2023. He was always knowledgedable, professional, reliable and overall pleasure to work with. I highly recommend Nikos.”
—Dr. Atis Elsts, senior researcher at Chaos Labs

“Solid development skills. When Nikos submits a pull request, it is a cold day in hell that it doesn't work.”
—Kevin Bennett, co-founder and CTO of KBMax

“One of the best developers I've ever worked with is @nikosbaxevanis. Please don't steal him from my team!”
—Mark Seemann, author of Dependency Injection Principles, Practices, and Patterns

Contact

Contact me about software-related topics via Email, 𝕏, GitHub, or Telegram. For encrypted email, you can use my PGP key. For Signal, email me and ask.